Figure 2. Passivation of QD surfaces via cation exchange.

(a) Absorption and photoluminescence (PL) spectra of the QDs before and after exposure to Zn-oleate at various temperatures after recapping with tert-butylamine (tBA). Inset: TEM image of 4.5 nm CuInSe_1.4S_0.6 QDs. Scale bar, 5 nm. (b) Current density versus voltage characteristics for QDs with varying degrees of Zn-cation exchange, or with ZnS SILAR post-treatment of the QD-infused anode (orange line). (c) Absorption and PL spectra of the QDs before and after exposure to Cd-oleate and recapping with tBA. (d) Current density versus voltage characteristics for QDs with varying degrees of Cd-cation exchange controlled by reaction temperature. The photovoltaic performance properties related to b and d can be found in Supplementary Tables S2 and S3.