Device fabrication and characterization of type-II CdTe submonolayer quantum dots embedded in ZnCdSe for the use in an intermediate band solar cell

Intermediate band (IB) photovoltaic devices are a new class of materials that have the potential of overcoming the Schockly-Quisser limit for single junction solar cells (SC), with the potential of achieving efficiencies as high as 63%. Previous proof of concept devices have been demonstrated using III-V materials; however, in these devices an unwanted decrease in the in the open circuit voltage limits device efficiency. To overcome these limitations, we propose an alternate system based on type-II CdTe/ZnCdSe sub-monolayer quantum dots (QDs) that have been shown to have promising properties for IBSCs. Here we analyze the I-V characteristics of refence SCs and QD-SCs. Reference SCs are made of an n-type region of Cl doped Zn_xCd_1-xSe , a p-type region of ZnSe_1-xTe_x doped with N, and an intrinsic region of Zn_xCd_1-xSe. The QD-SCs have CdTe sub-monolayer QDs embedded within the intrinsic region. To better understand the role of the IB two-step photon absorption is used in the QD-SC by performing photocurrent measurements coupled with an IR source. The QD-SC outperformed reference SC devices. The proposed system is viable material system for IBSC devices and we will discuss ways to improve effectiveness to achieve efficiencies.