Advancing wide-band-gap perovskite solar cells via vapor-phase deposition

Advancing wide-band-gap perovskite solar cells via vapor-phase deposition

SUMMARY

Wide-band-gap perovskite solar cells hold significant optoelectronic potential, with applications spanning building-integrated photovoltaics, large-area modules, and tandem solar cells. Vapor-phase deposition, leveraging its unique solvent-free processing, provides an ideal platform to address critical wide-band perovskite challenges, including halide segregation, phase instability, and defect control. This review critically assesses the vapor-phase technology landscape for wide-band perovskites. It first dissects fundamental physicochemical challenges in vacuum environments: mixed-halide lattice thermodynamic metastability, precursor sublimation kinetic mismatch, and complex organic cation volatility. It then systematically evaluates advanced deposition methodologies, ranging from sequential evaporation to hybrid vapor-solution routes, alongside optimization strategies spanning nucleation thermodynamics, bulk defect management, and interface energy alignment. It further examines the translation of material innovations into functional devices, highlighting vapor deposition's advantages in semitransparent cells, scalable modules, and high-efficiency perovskite silicon tandem cells, before outlining key challenges and future directions to guide both fundamental research and industrial-scale development.

INTRODUCTION

The urgent global demand for a low-cost, high-efficiency energy transition is the primary driver of research into perovskite solar cells, which have now reached a power conversion efficiency of twenty-seven percent toward commercialization. In this context, developing highly efficient and stable wide-band-gap perovskite thin films with an energy gap greater than one point six five electron volts is a central challenge for next-generation tandem solar cells. By integrating wide-band-gap top cells with crystalline silicon or narrow-band-gap perovskites, tandem solar cells can surpass the Shockley-Queisser limit of single-junction devices, as evidenced by the current record power conversion efficiency approaching thirty-five percent.

However, realizing high-performance wide-band-gap perovskites, particularly bromine-rich compositions, faces intrinsic material hurdles that are often poorly addressed by mainstream solution processing. The most prominent issues include light-induced halide segregation; high crystallization barriers, especially for all-inorganic systems such as cesium lead bromide; and the complexity of maintaining compositional homogeneity in multi-cation frameworks. These factors collectively lead to non-radiative recombination, phase instability, and uneven vertical distribution of components. While solution methods such as spin coating suffer from rapid, solvent-dependent crystallization and poor conformal coverage on textured substrates, vapor-phase deposition has emerged as a robust alternative. As a solvent-free dry process, vapor deposition enables precise control over precursor transport and surface reaction physics, offering superior large-area uniformity, accurate stoichiometry control, and excellent conformality on complex morphologies.

This review systematically examines the evolution of vapor-phase deposition for high-performance wide-band-gap perovskite photovoltaics. We first delineate the unique thermodynamic and kinetic challenges of solvent-free crystallization, followed by a comprehensive classification of vapor-based methodologies, ranging from traditional co-evaporation to emerging combinatorial and epitaxial techniques. We then categorize optimization strategies for defect mitigation and interface modulation and highlight the decisive advantages of these techniques in semitransparent cells and monolithic tandem devices. Finally, we provide a strategic outlook on overcoming the throughput-quality trade-offs to facilitate the gigawatt-scale implementation of perovskite-based tandem technologies.