Research Reveals Eco-Friendly Boost for PSC Quality

Abstract

In contrast to the substantial efforts dedicated to additive engineering in the field of perovskite solar cells (PSCs), the exploration of volatile solid additives has received surprisingly little attention. This study introduces a novel approach for fabricating highly efficient and stable PSCs by employing "naturally sourced volatile solid additives" (CP and CQ), which exhibit distinct volatilization rates and varying degrees of Lewis base-acid interactions with perovskite. During the PSC fabrication process involving two-stage thermal annealing, CP completely volatilized after the initial annealing step, resulting in the formation of a densely packed PbI2 film. Conversely, owing to its robust Lewis base-acid interaction with perovskite through bidentate coordination, a certain amount of CQ tends to persist after the first annealing step. However, no residue was observed after the second annealing step (stepwise-volatilization mechanism). This process yields high-quality FA-based perovskite crystallinity characterized by large-grained perovskite and highly preferred crystallite orientation. Consequently, CQ-based PSCs achieve a promising power conversion efficiency (PCE) of 25.00% (independently certified at 24.89%) with exceptional MPPT stability (PCE retention of 90.1% after 1000 h, ISOS-L-1). This study underscores the viability of the naturally sourced volatile solid additives for ecofriendly manufacturing of PSCs.

A recent breakthrough demonstrates how a substance derived from camphor (CP), a natural extract from the camphor tree, can significantly improve the quality of perovskite thin films used in solar cells. This material's sublimation property-its ability to transition directly from solid to gas without leaving residues-has been harnessed to enhance device performance and manufacturing efficiency.

The research team led by Professor Changduk Yang at the School of Energy and Chemical Engineering at UNIST announced that they successfully synthesized high-quality perovskite films by incorporating camphor derivatives. The absence of residual substances is expected to extend the lifespan and efficiency of solar cells while simplifying fabrication processes and reducing production costs.

Perovskite thin films in solar cells are composed of numerous crystal grains. Larger, well-ordered crystal grains facilitate smoother electron flow and strengthen structural integrity, leading to improved efficiency and durability. To achieve such high-quality structures, additives are often employed during fabrication; however, residual additives can sometimes hinder device performance.

To address this issue, the researchers utilized camphorquinone (CQ) as an additive. CQ is a derivative of camphor, which is extracted from the camphor tree, modified with an oxidation group. Unlike camphor, which sublimates directly from solid to gas, CQ undergoes stepwise sublimation-initially assisting in uniform seed crystal formation during the first thermal treatment, then gradually sublimating completely during the second heating process. This controlled sublimation allows the perovskite film to grow optimally without residual contaminants.

Researcher Jeewon Park, the first author of the study, explained, "CQ can be precisely timed to influence the crystal growth phase and leaves no residual material in the film. This unique property enabled us to produce high-quality perovskite films."

Solar cells fabricated with these CQ-enhanced films demonstrated a power conversion efficiency (PCE) of 25.2%, surpassing the 23.0% efficiency of control devices without additives-an improvement of approximately 9.6%. Under Maximum Power Point Tracking (MPPT) testing, which simulates real-world operating conditions, these devices retained over 90% of their initial efficiency after 1,000 hours, more than doubling the operational lifespan of comparable control devices. MPPT is a rigorous standard that evaluates the stability of solar cells under simulated sunlight.

Professor Yang emphasized the significance of this development: "Solving stability issues in perovskite solar cells (PSCs) using eco-friendly, naturally derived materials not only advances sustainable energy technology but also paves the way for more durable, cost-effective solar solutions."

This research has been published in the renowned journal Energy & Environmental Science (IF: 30.8) on June 21, 2025. The project was supported by the Ministry of Science and ICT (MSIT), the National Research Foundation of Korea (NRF), the Korea Energy Technology Evaluation Institute, and the Ministry of Trade, Industry and Energy (MOTIE).

Journal Reference

Jeewon Park, Seoyoung Kim, Wonjun Kim, et al., "Stepwise volatilization induced by nature-sourced volatile solid additives improving the efficiency and stability of perovskite solar cells," Energy Environ. Sci., (2025)