Perovskite solar cells (PSCs) have rapidly emerged as a front-runner in next-generation photovoltaic technologies, boasting a certified power conversion efficiency (PCE) of 26.95%—now rivaling crystalline silicon and CIGS cells. Yet, a critical bottleneck remains: energy losses stemming from mismatched energy levels between the perovskite absorber and charge transport layers (electron transport layers, ETLs; hole transport layers, HTLs), which hinder charge separation and transport. To address this, a team of researchers from Nanjing Tech University has published a landmark review in Nano-Micro Letters , systematically analyzing strategies to optimize energy-level alignment in PSCs from an energy flow perspective. This work offers a unified framework for minimizing energy loss and guiding the design of high-performance, stable PSCs.
Why Energy-Level Matching Matters for PSCs
At the heart of PSC inefficiency lies poor coordination between the energy levels of the perovskite absorber (ABX 3 structure) and its adjacent transport layers. When energy levels are misaligned, three critical issues arise:
The review emphasizes that resolving these issues requires a holistic understanding of energy flow—from photon absorption in the perovskite to charge extraction via ETLs/HTLs. By optimizing energy-level alignment, researchers can unlock PSCs’ full potential, bridging the gap between theoretical and experimental efficiencies.
Core Strategies for Energy-Level Optimization
The review categorizes energy-level tuning strategies into two key areas: optimizing the perovskite absorber itself and engineering ETL/HTL interfaces. Each approach targets specific energy loss pathways, with real-world case studies validating their effectiveness.
1. Perovskite Absorber Engineering: Tuning Bandgaps and Stability
The perovskite’s ABX 3 crystal structure (A: monovalent cation, B: divalent cation, X: halide anion) is highly tunable, enabling precise control of its bandgap and energy levels:
These modifications not only optimize energy levels but also improve stability—addressing a long-standing challenge for PSCs. For example, Cs-doped FA-based perovskites resist phase transitions under heat and moisture, extending device lifetimes.
2. ETL Engineering: Reducing Electron Transport Barriers
ETLs play a critical role in extracting electrons from the perovskite’s CBM while blocking hole backflow. The review highlights two dominant strategies for ETL optimization:
3. HTL Engineering: Optimizing Hole Extraction
HTLs must efficiently extract holes from the perovskite’s VBM while preventing electron leakage. The review details how molecular design and interface modification drive HTL performance:
Future Outlook: Toward System-Level Optimization
While individual strategies have made significant gains, the review argues that future progress will require system-level engineering—integrating multiple approaches to address efficiency, stability, and scalability simultaneously:
The review also highlights the need for more precise characterization tools—such as in-situ XPS and transient absorption spectroscopy—to better understand energy dynamics at interfaces. By merging theoretical modeling with experimental validation, researchers can accelerate the development of next-generation PSCs.
Stay updated on the latest breakthroughs from the Nanjing Tech University team as they continue to push the boundaries of perovskite photovoltaics!
Nano-Micro Letters
Experimental study
Strategies for Enhancing Energy‑Level Matching in Perovskite Solar Cells: An Energy Flow Perspective
24-Jun-2025