Enhancing the Performance of the Half Tin and Half Lead Perovskite Solar Cells by Suppression of the Bulk and Interfacial Charge Recombination

Abstract

In this article it is investigated how the hole extraction layer (HEL) influence the charge recombination and performance in half tin and half lead (FASn Pb I ) based solar cells (HPSCs). FASn Pb I film grown on PEDOT:PSS displays a large number of pin-holes and open grain boundaries, resulting in a high defect density and shunts in the perovskite film causing significant bulk and interfacial charge recombination in the HPSCs. By contrast, FASn Pb I films grown on PCP-Na, an anionic conjugated polymer, show compact and pin-hole free morphology over a large area, which effectively eliminates the shunts and trap states. Moreover, PCP-Na is characterized by a higher work function, which determines a favorable energy alignment at the anode interface, enhancing the charge extraction. Consequently, both the interfacial and bulk charge recombination in devices using PCP-Na HEL are considerably reduced giving rise to an overall improvement of all the device parameters. The HPSCs fabricated with this HEL display power conversion efficiency up to 16.27%, which is 40% higher than the efficiency of the control devices using PEDOT:PSS HEL (11.60%). Furthermore, PCP-Na as HEL offers superior performance in larger area devices compared to PEDOT:PSS.

Low‐Bandgap Mixed Tin‐Lead Perovskites and Their Applications in All‐Perovskite Tandem Solar Cells

“…k) Reverse and forward J–V curves and l) EQE spectra of PSCs deposited on PEDOT:PSS and PCP‐Na HTLs. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…Shao et al reported that using PCP‐Na could improve the mixed Sn‐Pb film quality and the corresponding device performance . They claimed that FASn 0.5 Pb 0.5 I 3 perovskite films fabricated on PEDOT:PSS substrates have pinholes with poor coverage, which increases the risks of charge recombination and leakage current.…”

Tin Halide Perovskites: Progress and Challenges

“…c) Schematic illustration comparing charge recombination (depicted with black arrow) processes in devices based on PEDOT:PSS and PCP‐Na hole extraction layers (HEL). Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

Realizing High Efficiency over 20% of Low‐Bandgap Pb–Sn‐Alloyed Perovskite Solar Cells by In Situ Reduction of Sn4+

“…Many efforts have been devoted to improving the PCE of low‐bandgap mixed Pb–Sn PSCs . However, it often exhibits a larger open‐circuit voltage ( V oc ) loss, and therefore, its efficiency is far behind that of pure Pb‐based PSCs with a medium bandgap.…”