Chen, Chia‐YuanChia‐YuanChenChang, Yu‐FanYu‐FanChangShih, Yen‐ChenYen‐ChenShihLiu, Ying‐ChuanYing‐ChuanLiuChiu, Chi‐FengChi‐FengChiuDinarlita, Rahma RahayuRahma RahayuDinarlitaTsai, Tsung‐YuTsung‐YuTsaiHung, Chieh‐MingChieh‐MingHungCha, Hou‐ChinHou‐ChinChaChen, You‐RenYou‐RenChenHuang, Zhi‐HaoZhi‐HaoHuangZhang, Yu‐ChengYu‐ChengZhangLin, Hui‐ChiehHui‐ChiehLinChu, Wei‐ChenWei‐ChenChuChiu, Wei‐HaoWei‐HaoChiuLi, Sie‐RongSie‐RongLiChang, Ting‐JuiTing‐JuiChangLiao, Yi‐HongYi‐HongLiaoRahayu, Siti UtariSiti UtariRahayuHan, Bo‐YuBo‐YuHanLin, Yun‐TouYun‐TouLinWang, Pei‐LingPei‐LingWangLiao, Zi‐TingZi‐TingLiaoTsai, Jhao‐YunJhao‐YunTsaiShi, Zhong‐EnZhong‐EnShiHsu, Chia‐TseChia‐TseHsuHsu, Po‐ShunPo‐ShunHsuChen, Po‐YuanPo‐YuanChenLi, Jia‐ZhenJia‐ZhenLiThakran, AnjaliAnjaliThakranChen, Yu‐TingYu‐TingChenLi, Yu‐ShengYu‐ShengLiYu, Hao‐WeiHao‐WeiYuGuo, Tzung‐FangTzung‐FangGuoCHU-CHEN CHUEHChu, Chih‐WeiChih‐WeiChuLEE-YIH WANGChen, Fang‐ChungFang‐ChungChenChen, Chih‐PingChih‐PingChenKUO-CHUAN HOTai, YianYianTaiLi, Chun‐TingChun‐TingLiLee, Ming‐WayMing‐WayLeeWang, Chih‐LiangChih‐LiangWangSun, Shih‐ShengShih‐ShengSunLee, Kun‐MuKun‐MuLeeTseng, Zong‐LiangZong‐LiangTsengHuang, Yu‐ChingYu‐ChingHuangChou, Pi‐TaiPi‐TaiChouKo, Chung‐WenChung‐WenKoWu, Chun‐GueyChun‐GueyWu2025-11-252025-11-252025https://www.scopus.com/record/display.uri?eid=2-s2.0-105018519720&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/734122Organic-thin film and perovskite solar cells are extremely promising because of their rapid progress in photovoltaic conversion efficiency (PCE). Beyond developing new materials and fabrication techniques, accurate performance characterization is essential for research and application. This study reports a round-robin interlaboratory comparison of current density–voltage (J–V) characteristics under standard test conditions (STC) and external quantum efficiency (EQE) spectra for large-area (>1 cm2) organic thin-film, perovskite, as well as reference solar cells with distinct spectral responses. Among 20 participating laboratories, the relative deviation in PCE of the samples reaches an unprecedented 111%. A comprehensive analysis identifies critical obstacles to measurement accuracy, including total incident irradiance for the samples, EQE spectrum measurements for spectral mismatch factors (SMM), temperature control, and methodologies for obtaining the J–V curves. Based on these findings, corresponding recommendations are presented to enhance the accuracy of performance characterization for emerging solar cells.falseorganic thin-film photovoltaics (OPV)perovskite solar cells (PSC)round-robin intercomparisonspectral mismatch factor (SMM)standard test conditions (STC)[SDGs]SDG7journal article10.1002/solr.2025005382-s2.0-105018519720