The Polymer Society of Korea

정인아 (포항공과대학교)

조창순 (포항공과대학교)

Perovskite solar cells offer high power conversion efficiencies with cost-effective fabrication, and their performance depends on efficient charge collection enabled by rapid carrier diffusion. Yet, earlier reports of low diffusion coefficients have conflicted with the near-unity charge collection observed in working devices, largely due to incomplete understanding of nanoscale charge dynamics.

Here, we summarize our recent work using a four-dimensional (x, y, z, t) carrier-tracking technique to quantitatively visualize vertical charge diffusion. We find strongly different diffusion coefficients in intragrain and intergrain regions, and show that both direct intragrain transport and detour pathways across grains contribute to efficient collection. While conventional methods estimate diffusivities of ~0.02 cm²/s, 4D tracking reveals ~0.25 cm²/s, resolving the longstanding discrepancy and explaining the strong device performance. These insights further suggest that improved control of polycrystalline growth could enable micrometer-thick perovskite layers that combine long optical paths with efficient charge collection.