PL R S ℏω exc. EL Intensity (arb. units) Energy (eV) Figure S1 – Kroutvar et al  t=12µs (a) (b)   exc.   QD EFEF EFEF V read CB VB Write Readout tt   exc.   QD VB CB   exc.   QD (d) (c)

Agilent 81104A Rise time 3ns Frequency: 0.25 – 100kHz PicoQuant 954nm Jobin Yvon Triax 550 Pulse generator Laser diode Spectrometer  <0.2nm Laser Voltage Detector Time ON OFF ON OFF V read =1.0V V store =-1.2V tt Repetition rate SPC Response time 0.2ns SPCM-AQR-16   exc.   QD p-contact Figure S2 – Kroutvar et al 1µs.5µs.3µs

Figure S3 – Kroutvar et al Energy (eV) EL Intensity (arb. units) Ti:Sa   exc. (eV)

Figure S4 – Kroutvar et al  store (90K)=(60±5)µs  store (100K)=(30±5)µs  store (10K) »1ms

  exc. ++   QD Bright exciton J z = -1 or ++   QD Dark exciton J z = -2 ++  Excitation tt Storage Readout QDContact Bright exciton J z = -1   QD CB VB Bright exciton J z = -1 Figure S5 – Kroutvar et al (a) (b) (c)