Effect of built-in electric field in photovoltaic InAs quantum dot embedded GaAs solar cell
2011 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 103, no 2, 335-341 p.Article in journal (Refereed) Published
In this paper, three p-i-n GaAs solar cells were grown and characterized, one with InAs quantum dot (QD) layers embedded in the depletion region (sample A), one with QD layers embedded in the n (-) base region (B), and the third without QDs (control sample C). QD-embedded solar cells (samples A and B) show broad photoluminescence spectra due to QD multi-level emissions but have lower open-circuit voltages V (oc) and lower photovoltaic (PV) efficiencies than sample C. On the other hand, the short-circuit current density J (sc) in sample A is increased while it is decreased in sample B. Theoretical analysis shows that in sample B where the built-in electric field in QDs is zero, electrons tend to occupy QDs and strong potential variations exist around QDs which deteriorate the electron mobility in the n (-) base region so that J (sc) in sample B is decreased. Hole trapping and electron-hole recombination in QDs are also enhanced in sample B, resulting in a reduced V (oc) and thus a worse PV effect. In sample A, a strong built-in field exists in QD layers, which facilitates photo-carrier extraction from QDs and thus J (sc) is increased. However, QDs in the depletion region in sample A act also as recombination-generation centers so that the dark saturated current density is drastically increased, which reduces V (oc) and the total PV effect. In conclusion, a nonzero built-in electric field around QDs is vital for using QDs to increase the PV effect in conventional p-i-n GaAs solar cells.
Place, publisher, year, edition, pages
2011. Vol. 103, no 2, 335-341 p.
IdentifiersURN: urn:nbn:se:kth:diva-33251DOI: 10.1007/s00339-010-6152-8ISI: 000289558900013ScopusID: 2-s2.0-79955852769OAI: oai:DiVA.org:kth-33251DiVA: diva2:414621
QC 201105042011-05-042011-05-022012-05-07Bibliographically approved