CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Solar revenues	$ 0	$ 296	$ 95	$ 433
Cost of solar revenues	0	141	72	227
Gross profit	0	155	23	206
Operating expenses:
Research and development	51,473	9,482	118,092	44,733
Selling, general, and administrative	65,826	3,693	117,886	15,538
Total operating expenses	117,299	13,175	235,978	60,271
Loss from operations	(117,299)	(13,020)	(235,955)	(60,065)
Other income (expense):
Interest income, net	172	411	259	1,082
Revaluation of Series A redeemable convertible preferred stock warrant liability	0	(2,844)	0	(3,339)
Loss on forward contract liability	0	0	(1,324)	0
Other income (expense), net	(340)	85	(251)	95
Loss before income taxes	(117,467)	(15,368)	(237,271)	(62,227)
Income tax expense	2	146	4	150
Net loss	(117,469)	(15,514)	(237,275)	(62,377)
Less: Premium on repurchase of redeemable convertible preferred stock	0	0	(13,407)	0
Net loss attributable to common stockholder, basic	(117,469)	(15,514)	(250,682)	(62,377)
Net loss attributable to common stockholder, diluted	$ (117,469)	$ (15,514)	$ (250,682)	$ (62,377)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.31)	$ (0.06)	$ (0.79)	$ (0.24)
Weighted-average shares used to compute net loss per share to common stockholders, basic and diluted (in shares)	377,660,477	260,534,724	318,315,891	260,449,607