Minimized Energy Loss at the Buried Interface of p‐i‐n Perovskite Solar Cells via Accelerating Charge Transfer and Forming p–n Homojunction

Abstract

The energy loss (Eloss) aroused by inefficient charge transfer and large energy level offset at the buried interface of p‐i‐n perovskite solar cells (PVSCs) limits their development. In this work, a BF4− anion‐assisted molecular doping (AMD) strategy is first proposed to improve the charge transfer capability of hole transport layers (HTLs) and reduce the energy level offset at the buried interface of PVSCs. The AMD strategy improves the carrier mobility and density of poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl) amine] (PTAA) and poly[N,N′‐bis(4‐butilphenyl)‐N,N′‐bis(phenyl)‐benzidine] (Poly‐TPD) HTLs while lowering their Fermi levels. Meanwhile, BF4− anions regulate the crystallization and reduce donor‐type iodine vacancies, resulting in the energetics transformation from n‐type to p‐type on the bottom surface of perovskite film. The faster charge transfer and formed p–n homojunction reduce charge recombination and Eloss at the HTL/perovskite buried interface. The PVSCs utilizing AMD treated PTAA and Poly‐TPD as HTLs demonstrate a highest power conversion efficiency (PCE) of 24.26% and 22.65%, along with retaining 90.97% and 85.95% of the initial PCE after maximum power point tracking for 400 h. This work provides an effective way to minimize the Eloss at the buried interface of p‐i‐n PVSCs by accelerating charge transfer and forming p–n homojunctions.

p-Toluenesulfonic Acid Modified Two-Dimensional ZrSe2 as a Hole Transport Layer for High-Performance Organic Solar Cells

“…When n approaches 1, it indicates that bimolecular recombination plays a dominant role, whereas trap-assisted recombination is inhibited, leading to higher FF and higher PCE. When n approaches 2, it indicates that bimolecular recombination is inhibited and trap-assisted recombination plays a dominant role, resulting in lower FF and lower PCE. , As shown in Figure e and Figure S11e, the n values of devices with ZrSe 2 , ZrSe 2 :PTSA, PEDOT:PSS, and ITO HTLs are 1.28, 1.24, 1.18, and 1.44, respectively. Among them, the n of the device with ZrSe 2 :PTSA HTL is lower than that of the device with the original ZrSe 2 HTL, indicating that the trap-assisted recombination of ZrSe 2 is more effectively inhibited after modification with PTSA.…”

Improved Air Stability for High-Performance FACsPbI3 Perovskite Solar Cells via Bonding Engineering

“…Due to the weak bonding in Pb−I bonds, iodine ions are easy to migrate under the influence of environmental stress, which will leave a large number of donor-type V I vacancy defects on the surface of the perovskite film, leading to a more n-type perovskite surface. 7 Therefore, PT molecules can regulate and passivate V I defects to make the energy-level structure of the perovskite surface shift downward. Compared with the control film, the CBM of the PT-modified perovskite film is closer to the lowest unoccupied molecular orbital level of the PCBM ETL (−4.20 eV), indicating a smaller electron transport barrier.…”

“…Based on the linear intersection method and band gap values, the conduction band minimum (CBM)/valence band maximum (VBM) values of the control and PT-modified perovskite films can be estimated as −4.04/–5.59 and −4.12/–5.66 eV, respectively. , Therefore, the energy-level diagrams of the control and PT-modified perovskite films are revealed in Figure f, and the detailed parameter values are summarized in Table S1. Due to the weak bonding in Pb–I bonds, iodine ions are easy to migrate under the influence of environmental stress, which will leave a large number of donor-type V I vacancy defects on the surface of the perovskite film, leading to a more n-type perovskite surface . Therefore, PT molecules can regulate and passivate V I defects to make the energy-level structure of the perovskite surface shift downward.…”

“…In recent years, organic–inorganic hybrid perovskite solar cells (PSCs) are becoming a research hotspot in the field of photovoltaic energy, because their certified photoelectric conversion efficiency (PCE) has reached 26.1%, which is equivalent to that of commercial silicon-based solar cells. – The realization of this excellent PCE can be attributed to the numerous advantages of perovskite crystals, including broad spectral response, tunable optical band gap, high defect tolerance, small exciton binding energy, long carrier diffusion distance, and so forth. – However, the weak binding and ion–electron characteristics of perovskite crystals inevitably cause high-density defects, which leads to significant nonradiation recombination and reduces the overall reliability of the device. , …”

A ZnO&GeSe composite electron transport layer for organic solar cells

“…The relationship between J sc and light intensity can be expressed by the formula J sc ∝ I α . 40 The closer the value of α tends to 1, the more likely the bimolecular recombination probability of OSCs tends to be 0. The fitted J sc –light intensity dependence curve is shown in Fig.…”