Chemical Reduction of Intrinsic Defects in Thicker Heterojunction Planar Perovskite Solar Cells

Abstract

Minimization of defects in absorber materials is essential for hybrid perovskite solar cells, especially when constructing thick polycrystalline layers in a planar configuration. Here, a simple methylamine solution-based additive is reported to improve film quality with nearly an order of magnitude reduction in intrinsic defect concentration. In the resultant film, an increase in carrier lifetime as a result of a decrease in shallow electronic disorder is observed. This superior crystalline film quality is further evidenced via a doubled spin relaxation time as compared with other reports. Bearing sufficient carrier diffusion length, a thick absorber layer (≈650 nm) is implemented in planar devices to achieve a champion power conversion efficiency of 20.02% with a stabilized output efficiency of 19.01% under one sun illumination. This work demonstrates a simple approach to improve hybrid perovskite film quality by substantial reduction of intrinsic defects for wide applications in optoelectronics.

Gas-solid reaction based over one-micrometer thick stable perovskite films for efficient solar cells and modules

“…A high-quality thick perovskite film is desirable to achieve a high device yield and reproducibility in making large-area solar modules. Besides, thicker perovskite films can not only improve the light harvesting 13,14 , but also broaden light response region by utilizing the below-band absorption 15 . As such, it is advantageous to construct a high-quality thick perovskite film with enough carrier diffusion length in PSCs to endorse both higher efficiency and manufacturing viability.…”

“…This gas−solid reaction-based method introduces a liquid intermediate, which leads to induced morphology reconstruction, defects healing 19,20 . Meanwhile, CH 3 NH 2 gas treatment can help reduce the defect density in perovskite films 19,20 and also elimination of I 2 13 . Besides, CH 3 NH 2 -induced δ-NH 2 CH=NH 2 PbI 3 in (CH 3 NH 3 ) x (NH 2 CH=NH 2 ) 1− x PbI 3 is also reported to passivate trap states to improve device performance 21 .…”

“…These earlier works have inspired us to combine the CH 3 NH 2 gas-based perovskite formation method and partial substitution of iodine ions by chorine ions to fabricate high quality over 1-μm-thick perovskite films with a sufficient charge diffusion length, which is not only beneficial for better light absorbing but also desirable for fabricating large-area solar modules with high yield and reproducibility via low-cost printing techniques 13,32 .…”

Simultaneous Evolution of Uniaxially Oriented Grains and Ultralow-Density Grain-Boundary Network in CH3NH3PbI3 Perovskite Thin Films Mediated by Precursor Phase Metastability

“…As shown in Figure 5B, the trap-filling limited voltage (V TFL ) is determined by the kink point where the current increase becomes nonlinear. 27 The relationship between V TFL and N is given by the equation,…”

“…27 The values of N in the MAPbI 3 ·MACl·xCH 3 NH 2 -derived MAPbI 3 , respectively. The reduced N in the MAPbI 3 ·MACl·xCH 3 NH 2 -derived MAPbI 3 thin film is in good agreement with the prolonged PL lifetime.…”