Enhanced charge carrier mobility and lifetime suppress hysteresis and improve efficiency in planar perovskite solar cells (original) (raw)
Applied Materials Today, 2016
Hybrid perovskites have emerged as the most promising thin-film photovoltaic technology with efficiencies exceeding 20% merely in the last five years. Most highefficiency perovskite solar cells reported in the recent years have relatively small device area in comparison to that required for commercial photovoltaic modules. While these results are excellent from an academic perspective, scaling up the overall cell device area is crucial for achieving practical utility for hybrid perovskite based thin-film solar cells. In this paper, we present a comprehensive study on the use of temperature-controlled doctor blading technique for the growth of large island, crystalline perovskite thin-films. Specifically, we elucidate the physical conditions such as substrate temperature, solution volume, and blade speed under ambient conditions that control the growth of large area perovskite thin-films with desired island size, thickness, uniformity and crystallinity. Using these doctor-bladed thin-films we fabricated devices of ~1 cm 2 area in air that yielded an average efficiency of 7.32% with negligible hysteresis in the current-voltage scans. Further improvements in efficiency can be expected by reproducing the perovskite thin-film growth using doctor-blading in a controlled environment, through compositional tuning of the band-gap, or by selecting electron and hole transport layers with better band alignment with the perovskite electronic energy level.
Highly efficient planar perovskite solar cells through band alignment engineering
Energy Environ. Sci., 2015
The simplification of perovskite solar cells (PSCs), by replacing the mesoporous electron selective layer (ESL) with a planar one, is advantageous for large-scale manufacturing. PSCs with a planar TiO 2 ESL have been demonstrated, but these exhibit unstabilized power conversion efficiencies (PCEs). Herein we show that planar PSCs using TiO 2 are inherently limited due to conduction band misalignment and demonstrate, with a variety of characterization techniques, for the first time that SnO 2 achieves a barrier-free energetic configuration, obtaining almost hysteresis-free PCEs of over 18% with record high voltages of up to 1.19 V.
Unraveling film transformations and device performance of planar perovskite solar cells
Nano Energy, 2015
High performance (415%) organometaltrihalide based solar cells have been demonstrated in recent years to be a promising candidate for low cost photovoltaics and have attracted significant attention in the photovoltaic community. Planar thin film perovskite solar cells, which are more easily fabricated, provide a great platform to investigate the perovskite film properties. Until now, many of the properties of perovskite thin films remain unexplored and the link between film properties and device performances is in need of investigation to further boost the efficiencies of these devices. Here, film transformation of perovskite materials is demonstrated as a critical factor to reach high performance in planar heterojunction CH 3 NH 3 PbI 3 À x Cl x solar cells. Reaction induced secondary phases can be observed and carefully controlled by tuning the processing conditions during film formation. The properties of CH 3 NH 3 PbI 3 À x Cl x films are investigated and a possible formation pathway is proposed. It is shown that the high performance devices are attainable with a small portion of secondary phases coexisting with CH 3 NH 3 PbI 3 film and power conversion efficiencies of up to 14% are achieved. The correlations between the phases present, device performance and physical properties are discussed to identify the role of the secondary phases in CH 3 NH 3 PbI 3 À x Cl x material.
Nano Research, 2014
We demonstrate that charge carrier diffusion lengths of two classes of perovskites, CH 3 NH 3 PbI 3-x Cl x and CH 3 NH 3 PbI 3 , are both highly sensitive to film processing conditions and optimal processing procedures are critical to preserving the long carrier diffusion lengths of the perovskite films. This understanding, together with the improved cathode interface using bilayer-structured electron transporting interlayers of [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM)/ZnO, leads to the successful fabrication of highly efficient, stable and reproducible planar heterojunction CH 3 NH 3 PbI 3-x Cl x solar cells with impressive power-conversion efficiencies (PCEs) up to 15.9%. A 1-square-centimeter device yielding a PCE of 12.3% has been realized, demonstrating that this simple planar structure is promising for large-area devices.
Universal Approach toward Hysteresis-Free Perovskite Solar Cell via Defect Engineering
Journal of the American Chemical Society, 2018
Organic-inorganic halide perovskite is believed to be a potential candidate for high efficiency solar cells because power conversion efficiency (PCE) was certified to be more than 22%. Nevertheless, mismatch of PCE due to current density (J)-voltage (V) hysteresis in perovskite solar cells is an obstacle to overcome. There has been much lively debate on the origin of J-V hysteresis; however, effective methodology to solve the hysteric problem has not been developed. Here we report a universal approach for hysteresis-free perovskite solar cells via defect engineering. A severe hysteresis observed from the normal mesoscopic structure employing TiO2 and spiro-MeOTAD is almost removed or does not exist upon doping the pure perovskites, CH3NH3PbI3 and HC(NH2)2PbI3, and the mixed cation/anion perovskites, FA0.85MA0.15PbI2.55Br0.45 and FA0.85MA0.1Cs0.05PbI2.7Br0.3, with potassium iodide. Substantial reductions in low-frequency capacitance and bulk trap density are measured from the KI-dope...
Latvian Journal of Physics and Technical Sciences, 2017
Organometal halide perovskites are promising materials for lowcost, high-efficiency solar cells. The method of perovskite layer deposition and the interfacial layers play an important role in determining the efficiency of perovskite solar cells (PSCs). In the paper, we demonstrate inverted planar perovskite solar cells where perovskite layers are deposited by two-step modified interdiffusion and one-step methods. We also demonstrate how PSC parameters change by doping of charge transport layers (CTL). We used dimethylsupoxide (DMSO) as dopant for the hole transport layer (PEDOT:PSS) but for the electron transport layer [6,6]-phenyl CThe highest main PSC parameters (
Functional materials, device architecture, and flexibility of perovskite solar cell
Emergent Materials, 2018
Perovskite solar cells (PSCs) are an emerging photovoltaic technology that promises to offer facile and efficient solar power generation to meet future energy needs. PSCs have received considerable attention in recent years, have attained power conversion efficiencies (PCEs) over 22%, and are a promising candidate to potentially replace the current photovoltaic technology. The emergence of PSCs has revolutionized photovoltaic research and development because of their high efficiencies, inherent flexibility, the diversity of materials/synthetic methods that can be employed to manufacture them, and the various possible device architectures. Further optimization of material compositions and device architectures will help further improve efficiency and device stability. Moreover, the search for new functional materials will allow for mitigation of the existing limitations of PSCs. This review covers the recently developed advanced techniques and research trends related to this emerging photovoltaic technology, with a focus on the diversity of functional materials used for the various layers of PSC devices, novel PSC architectures, methods that increase overall cell efficiency, and substrates that allow for enhanced device flexibility.
Perovskites photovoltaic solar cells: An overview of current status
Renewable and Sustainable Energy Reviews, 2018
Perovskite based solar cells have recently emerged as one of the possible solutions in the photovoltaic industry for availing cheap solution processable solar cells. Hybrid perovskites display special combination of low bulktrap densities, ambipolar charge transport properties, good broadband absorption properties and long charge carrier diffusion lengths, which make them suitable for photovoltaic applications. The year 2015 witnessed an upsurge in the published research articles on perovskite solar cells (PSC) which is indicative of the potential of this material. Since the introduction of PSC the power conversion efficiency has reached above 22% in a relatively short period of time. However, the poor reproducibility in device fabrication and lack of uniformity of the PSCs performances is a major challenge in obtaining highly efficient large scale PSC devices. The aim of this paper is to present a brief review on the current status of perovskites based solar cell due to the use of different device architectures, fabrication techniques as well as on the use of various electron and hole interfacial layers (HTMs and ETMs). The review also discusses the basic mechanisms for device operation which provides better understanding on the properties of the various layers of device structures.
Low-temperature operation of perovskite solar cells: With efficiency improvement and hysteresis-less
Methylammonium lead iodide perovskite solar cells (PSCs) based on a solution-processed ZnO electron transporting layer were systematically investigated at low-temperature operating conditions. The power conversion efficiency gradually improved from 14.2% to 15.5% as the temperature decreased from 298 to 253 K, mainly owing to increments of short circuit current density and open circuit voltage. In addition, the improvements in photocurrent related to the high charge carrier mobility, owing to the ideal non-dispersive charge transport and fast electron transport lifetime at low temperature. Strikingly, hysteresis was suppressed with decreasing temperature related to the inhibition or relatively slow of ionic migration at reversed poling direction. This finding shows promising result of PSCs working efficiently under low temperature condition.