Light-intensity-dependent photoresponse time of organic photodetectors and its molecular origin

Chiara Labanti, Jiaying Wu, Jisoo Shin, Saurav Limbu, Sungyoung Yun, Feifei Fang, Song Yi Park, Chul Joon Heo, Younhee Lim, Taejin Choi, Hyeong Ju Kim, Hyerim Hong, Byoungki Choi, Kyung Bae Park, James R. Durrant, Ji Seon Kim

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Organic photodetectors (OPDs) exhibit superior spectral responses but slower photoresponse times compared to inorganic counterparts. Herein, we study the light-intensity-dependent OPD photoresponse time with two small-molecule donors (planar MPTA or twisted NP-SA) co-evaporated with C60 acceptors. MPTA:C60 exhibits the fastest response time at high-light intensities (>0.5 mW/cm2), attributed to its planar structure favoring strong intermolecular interactions. However, this blend exhibits the slowest response at low-light intensities, which is correlated with biphasic photocurrent transients indicative of the presence of a low density of deep trap states. Optical, structural, and energetical analyses indicate that MPTA molecular packing is strongly disrupted by C60, resulting in a larger (370 meV) HOMO level shift. This results in greater energetic inhomogeneity including possible MPTA-C60 adduct formation, leading to deep trap states which limit the low-light photoresponse time. This work provides important insights into the small molecule design rules critical for low charge-trapping and high-speed OPD applications.

Original languageEnglish
Article number3745
JournalNature communications
Issue number1
Publication statusPublished - 2022 Dec
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • General
  • Physics and Astronomy(all)


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