Improving the performance of perovskite solar cells using a dual-hole transport layer

The energy loss (Eloss) caused by inefficient charge transfer and large energy level offset at the buried interface can easily restrict the performance of p-i-n perovskite solar cells (PVSCs). In this study, the utilization of poly-TPD and P3CT-N as a dual-hole transporting layer (HTLs) was implemented in a sequential manner. This approach aimed to improve the charge transfer efficiency of the HTL and mitigate charge recombination at the interface between the HTL and PVK. The results showed that this strategy also could achieve more suitable energy levels, improve the quality of the perovskite film layer, and ultimately enhance the device's stability. IPVSCs employing the dual-HTLs approach exhibited the highest power conversion efficiency of 19.85%, and the open-circuit voltage increased to 1.09 V from 1.00 V. This study offers a straightforward and efficient approach to boost the device performance by minimizing Eloss and reducing the buried interfacial defects. The findings underscore the potential of employing a dual-HTL strategy as a promising pathway for further advancements in PVSCs.

Magnetron sputtered ZnO electron transporting layers for high performance perovskite solar cells

An ideal electron transporting layer (ETL) of perovskite solar cells (PSCs) requires reasonable energy levels, high electrical conductivity and excellent charge extraction. The low processing temperature makes ZnO a promising ETL for PSCs; however the widely used solution-processed ZnO films often suffer from high-density surface defect states, which might cause severe charge recombinations at the ETL/perovskite interface and accelerate the chemical decomposition of perovskite materials. In this work, we employed the vacuum-based magnetron sputtering method to deposit ZnO ETLs, which significantly reduces the number of oxygen vacancies and hydroxyl groups on the ZnO surface. The magnetron sputtered ZnO based CH3NH3PbI3 PSCs yield a considerable power conversion efficiency (PCE) of 13.04% with excellent long-term device stability. Furthermore, aiming to improve the ETL/perovskite interface for more efficient electron extraction, a bilayer ZnO/SnO2 ETL was designed for constructing high-efficiency PSCs. The detailed morphology characterization confirms that the bilayer ZnO/SnO2 provides a low-roughness film surface for the deposition of high-quality perovskite films with full coverage and long-range continuity. The carrier dynamic study reveals that the presence of the SnO2 layer results in the formation of favorable cascade energy alignments and facilitates the electron extraction at the ETL/perovskite interface. As a result, compared with the ZnO-based PSCs, the device constructed with the bilayer ZnO/SnO2 ETL delivers an improved PCE of 15.82%, coupled with a reduced hysteresis.

Improved efficiency and carrier dynamic transportation behavior in perovskite solar cells with CuInS2 quantum dots as hole-transport materials

Inorganic quantum dot (QD)-based hole-transport materials (HTMs) have proved their potential in perovskite solar cells (PSCs). In this work, CuInS2 quantum dots (CIS QDs) were applied as HTMs for PSCs with the architecture of TiO2/Cs0.17FA0.83Pb(Br0.2I0.8)3/HTM/Au. By optimizing the preparation process, a high-quality perovskite thin film could be obtained. When the speed was 5000 rpm, the speed acceleration was 3000 rpm per s and heat treated at 150 °C, the perovskite film had low surface roughness (15.26 nm) and obvious grain boundary. The photoelectric conversion efficiency (PCE) of PSCs was greatly improved from 2.83% to 12.33% utilizing CIS QDs at an optimal concentration and with surface ligands as HTMs. Surface ligands can control the size and shape of CIS QDs, and thus affect the performance of PSCs. The carrier dynamic transportation behaviour at the CIS/perovskite interface was studied, which showed that CIS QDs as HTMs in PSCs can strongly quench the fluorescence and increase the photobleaching recovery rate. Therefore, CIS QDs are promising inorganic HTMs for the fabrication of PSCs.

Polarization-enhanced photoelectric performance in a molecular ferroelectric hexane-1,6-diammonium pentaiodobismuth (HDA-BiI5)-based solar device

Molecular ferroelectric HDA-BiI₅ has been utilized as the light-absorbing layer for organic-inorganic hybrid solar cells.

Highly efficient bifacial CsPbIBr2 solar cells with a TeO2/Ag transparent electrode and unsymmetrical carrier transport behavior

Bright red CsPbIBr₂ films possess intrinsic semitransparent features, which make them promising materials for smart photovoltaic windows, power curtain walls, top cells for tandem solar cells, and bifacial photovoltaics.

Self-doping synthesis of trivalent Ni2O3 as a hole transport layer for high fill factor and efficient inverted perovskite solar cells

We present a novel self-doping method to obtain trivalent nickel oxide (Ni₂O₃) as an HTL, and its excellent optical transmittance and hole extraction efficiencies lead to a PCE of 17.89% and high FF of 82.66%.

Tuning Methylammonium Iodide Amount in Organolead Halide Perovskite Materials by Post-Treatment for High-Efficiency Solar Cells

In this study, the composition of organic-inorganic perovskite materials is tuned by methylammonium iodide (MAI) post-treatment for high photovoltaic performance. By spin-coating MAI solutions of different concentrations, the amounts of PbI₂ and MAI in perovskite layers are tuned. In perovskites, the removal of PbI₂ through a reaction with MAI decreases the hysteresis in photocurrent density-voltage curves. Further, by treating perovskites with a high-concentration MAI solution, the excess MAI is incorporated into the perovskites. These perovskites with excess MAI show better power conversion efficiencies (of up to 20.7%) than perovskites with excess PbI₂ because of the decrease in trap density. Since the present post-treatment can control perovskite composition without affecting the morphology and crystallinity of the perovskite crystals, this technique would be a useful tool to improve the photovoltaic performance of perovskite solar cells.