ABSTRACT
The evolution of defects during perovskite film fabrication deteriorates the overall film quality and adversely affects the device efficiency of perovskite solar cells (PSCs). We endeavored to control the formation of defects by applying an additive engineering strategy using FABr, which retards the crystal growth formation of CsPbI2.2Br0.8 perovskite by developing an intermediate phase at the initial stage. Improved crystalline and pinhole-free perovskite film with an optimal concentration of FABr-0.8M% additive was realized through crystallographic and microscopic analysis. Suppressed non-radiative recombination was observed through photoluminescence with an improved lifetime of 125 ns for FABr-0.8M% compared to the control film (83 ns). The champion device efficiency of 17.95% was attained for the FABr-0.8M% PSC, while 15.94% efficiency was achieved in the control PSC under air atmospheric conditions. Furthermore, an impressively high indoor performance of 31.22% was achieved for the FABr-0.8M% PSC under 3200 K (1000 lux) LED as compared to the control (23.15%). With a realistic approach of air processing and controlling the crystallization kinetics in wide-bandgap halide PSCs, this investigation paves the way for implementing additive engineering strategies to reduce defects in halide perovskites, which can further benefit efficiency enhancements in outdoor and indoor applications.
ABSTRACT
Materials and processing of transparent electrodes (TEs) are key factors to creating high-performance translucent perovskite solar cells. To date, sputtered indium tin oxide (ITO) has been a general option for a rear TE of translucent solar cells. However, it requires a rather high cost due to vacuum process and also typically causes plasma damage to the underlying layer. Therefore, we introduced TE based on ITO nanoparticles (ITO-NPs) by solution processing in ambient air without any heat treatment. As it reveals insufficient conductivity, Ag nanowires (Ag-NWs) are additionally coated. The ITO-NPs/Ag-NW (0D/1D) bilayer TE exhibits a better figure of merit than sputtered ITO. After constructing CsPbBr3 perovskite solar cells, the device with 0D/1D TE offers similar average visible transmission with the cells with sputtered ITO. More interestingly, the power conversion efficiency of 0D/1D TE device was 5.64%, which outperforms the cell (4.14%) made with sputtered-ITO. These impressive findings could open up a new pathway for the development of low-cost, translucent solar cells with quick processing under ambient air at room temperature.
ABSTRACT
Recently, nickel oxide (NiOx) thin films have been used as an efficient and robust hole transport layer (HTL) in inverted planar perovskite solar cells (IP-PSCs) to replace costly and unstable organic transport materials. However, the power conversion efficiency (PCE) of most IP-PSCs using NiOx HTLs is rather limited below 20% due to insufficient electronic conductivity of the NiOx. In this work, solution-processed Al-doped NiOx (ANO) films are suggested as HTLs for low-cost and stable IP-PSCs. The electrical conductivity of the NiOx film is significantly enhanced by Al doping, which effectively reduces the nonradiative recombination losses at the HTL-perovskite interfaces and boosts hole extraction/transportation. The device with undoped NiOx shows the best PCE of 16.56%, whereas ANO HTL (5% doping) contributes to achieving a PCE of 20.84%, which outperforms other CH3NH3PbI3 IP-PSCs with NiOx-based HTLs reported to date. Moreover, a reliability test (1728 h storage) shows that the performance stability is enhanced by approximately 11% by employing ANO HTLs. This investigation into ANO HTLs provides a new guideline for the further development of highly efficient and reliable IP-PSCs using low-cost and robust metal oxide HTLs.
ABSTRACT
Adopting an efficient charge transport layer is crucial to improve the photovoltaic (PV) performances of organo-lead halide perovskite (PRV) solar cells. In this study, we suggest a novel hybrid hole-transport layer (HTL) consisting of single-walled carbon nanotubes (SWNTs) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) for inverted-planar PRV devices. The SWNTs were drop-cast on ITO/glass substrates, and they were partly grown perpendicular to the substrates. Then, we coated PEDOT:PSS to cover the SWNTs for complete electron-blocking. A PRV light-harvester was spin-cast on the hybrid HTL, and the vertical SWNTs protruded into the PRV through penetrating the PEDOT:PSS. Steady-state photoluminescence spectroscopy evidenced that the SWNTs/PEDOT:PSS hybrid HTL showed enhanced charge-carrier quenching properties. The hybrid HTL also revealed negligible parasitic absorption loss checked by UV-Vis spectroscopy. These contributed to improve the average power conversion efficiency from 9.4% to 11.0% (up to 12.5% for the best cell) based on fabricated 90 devices. Furthermore, significant suppression of current-voltage hysteresis was attained by employing the hybrid HTL. This study not only manifests unprecedented utilization of the SWNTs for the HTL in inverted planar PRV cells but also paves the way for the development of high-performance and reliable PRV solar cells compatible with flexible processing at low temperature (<150 °C).